Language pathology is a broad term, used to refer to the symptoms of speech and language speech and language disorders, the aetiologies of these disorders, and the methods and results of the disciplines which study them. The major disciplines involved are medicine, psychology, and linguistics (including speech science). It is neither possible nore desirable, in an inter-disciplinary field, to ignore the contribution of other sciences. Here, however, the concentration will be, so far as is feasible, on the distincitve role of linguistics in the investigation of language disorders. The term language disorder is used as a general label for any persistent non-normal linguistic behaivor in children or adults.